
<template>
    <el-color-picker
        v-model="theme"
        :predefine="['#409EFF', '#1890ff', '#304156','#212121','#11a983', '#13c2c2', '#6959CD', '#f5222d']"
        class="theme-picker"
        popper-class="theme-picker-dropdown"
    />
</template>

<script lang="ts">
    import { Component, Prop, Vue, Watch } from 'vue-property-decorator'
    import { SettingsModule } from '@/store/modules/settings'

    const version = require('element-ui/package.json').version // element-ui version from node_modules
    const ORIGINAL_THEME = '#409EFF' // default color

    @Component({
        name: 'ThemePicker'
    })
    export default class extends Vue {
        private chalk = '' // The content of theme-chalk css
        private theme = ''

        get defaultTheme() {
            return SettingsModule.theme
        }

        @Watch('defaultTheme', { immediate: true })
        private onDefaultThemeChange(value: string) {
            this.theme = value
        }

        @Watch('theme')
        private async onThemeChange(value: string) {
            if (!value) return
            const oldValue = this.chalk ? this.theme : ORIGINAL_THEME
            const themeCluster = this.getThemeCluster(value.replace('#', ''))
            const originalCluster = this.getThemeCluster(oldValue.replace('#', ''))
            const message = this.$message({
                message: '  Compiling the theme',
                customClass: 'theme-message',
                type: 'success',
                duration: 0,
                iconClass: 'el-icon-loading'
            })

            if (!this.chalk) {
                const url = `https://unpkg.com/element-ui@${version}/lib/theme-chalk/index.css`
                await this.getCSSString(url, 'chalk')
            }

            const getHandler = (variable: string, id: string) => {
                return () => {
                    const originalCluster = this.getThemeCluster(ORIGINAL_THEME.replace('#', ''))
                    const newStyle = this.updateStyle((this as any)[variable], originalCluster, themeCluster)

                    let styleTag = document.getElementById(id)
                    if (!styleTag) {
                        styleTag = document.createElement('style')
                        styleTag.setAttribute('id', id)
                        document.head.appendChild(styleTag)
                    }
                    styleTag.innerText = newStyle
                }
            }
            const chalkHandler = getHandler('chalk', 'chalk-style')
            chalkHandler()

            let styles: HTMLElement[] = [].slice.call(document.querySelectorAll('style'))
            styles = styles
                .filter(style => {
                    const text = style.innerText
                    return new RegExp(oldValue, 'i').test(text) && !/Chalk Variables/.test(text)
                })
            styles.forEach(style => {
                const { innerText } = style
                if (typeof innerText !== 'string') return
                style.innerText = this.updateStyle(innerText, originalCluster, themeCluster)
            })

            this.$emit('change', value)
            message.close()
        }

        private updateStyle(style: string, oldCluster: string[], newCluster: string[]) {
            let newStyle = style
            oldCluster.forEach((color, index) => {
                newStyle = newStyle.replace(new RegExp(color, 'ig'), newCluster[index])
            })
            return newStyle
        }

        private getCSSString(url: string, variable: string) {
            return new Promise(resolve => {
                const xhr = new XMLHttpRequest()
                xhr.onreadystatechange = () => {
                    if (xhr.readyState === 4 && xhr.status === 200) {
                        (this as any)[variable] = xhr.responseText.replace(/@font-face{[^}]+}/, '')
                        resolve()
                    }
                }
                xhr.open('GET', url)
                xhr.send()
            })
        }

        private getThemeCluster(theme: string) {
            const tintColor = (color: string, tint: number) => {
                let red = parseInt(color.slice(0, 2), 16)
                let green = parseInt(color.slice(2, 4), 16)
                let blue = parseInt(color.slice(4, 6), 16)
                if (tint === 0) { // when primary color is in its rgb space
                    return [red, green, blue].join(',')
                } else {
                    red += Math.round(tint * (255 - red))
                    green += Math.round(tint * (255 - green))
                    blue += Math.round(tint * (255 - blue))
                    return `#${red.toString(16)}${green.toString(16)}${blue.toString(16)}`
                }
            }

            const shadeColor = (color: string, shade: number) => {
                let red = parseInt(color.slice(0, 2), 16)
                let green = parseInt(color.slice(2, 4), 16)
                let blue = parseInt(color.slice(4, 6), 16)
                red = Math.round((1 - shade) * red)
                green = Math.round((1 - shade) * green)
                blue = Math.round((1 - shade) * blue)
                return `#${red.toString(16)}${green.toString(16)}${blue.toString(16)}`
            }

            const clusters = [theme]
            for (let i = 0; i <= 9; i++) {
                clusters.push(tintColor(theme, Number((i / 10).toFixed(2))))
            }
            clusters.push(shadeColor(theme, 0.1))
            return clusters
        }
    }
</script>

<style lang="scss">
    .theme-message,
    .theme-picker-dropdown {
        z-index: 99999 !important;
    }

    .theme-picker .el-color-picker__trigger {
        height: 26px !important;
        width: 26px !important;
        padding: 2px;
    }

    .theme-picker-dropdown .el-color-dropdown__link-btn {
        display: none;
    }
</style>
